Homopolymerized vinyl pyrrolidone has many uses in the pharmaceutical and cosmetic arts as well as in the field of copolymerization and crosslinking with various monomers for clarification of beverages. Vinyl pyrrolidone monomer, prepared by reacting acetylene with pyrrolidone or by reaction with ammonia and formaldehyde, results in a product containing from about 8 to about 0.5% impurities which are objectionable for many purposes including beverage clarification or pharmaceutical and cosmetic formulations. The current process for the preparation of vinyl pyrrolidone involves the vinylation of pyrrolidone with acetylene in the presence of a salt catalyst as described, for example, in U.S. Pat. No. 4,873,336. This process achieves a product in about 98 to 99.7% purity after recovery of product by fractional distillation. However, objectionable color and odor forming impurities, as well as polymer forming impurities, such as unreacted pyrrolidone, butene, butyne, butadiene and amine derivatives remain after distillation. These impurities in amounts above 0.5% are considered unsuitable for the above purposes; thus, product distillation is inadequate to meet the high purity requirements demanded in certain fields of application, particularly for the use of vinyl pyrrolidone polymers in medicine as plasma extenders and for cosmetics in hair fixation and other hair and skin treating applications. Requirements for beverage clarifiers are even more stringent, demanding less than a few parts per million of any taste or color altering contaminant.
Accordingly, it is an object of this invention to produce vinyl pyrrolidone in a purity of from about 99.95% to 100% by an economical and commercially feasible process.
A second object of this invention is to produce vinyl pyrrolidone in a high state of purity by a process which avoids the use of extraneous ionic chemicals as described in U.S. Pat. No. 5,039,817.
These and other objects will become apparent from the following description and disclosure.